Packaging methods for covering food products include, for example, home-use wrap packaging, overwrap packaging, twist wrapping, bag packaging, skin packaging, pillow shrink packaging, stretch packaging, and top seal packaging. In particular, continuous packaging machines enabled to handle pillow shrink packaging and top seal packaging are widely used because of their ability for high speed packaging and the quality of finished products.
Moreover, for environmental considerations, a growing trend of reducing waste, such as food waste from supermarkets, convenience stores, and the like, has lead to an increased focus on gas pack packaging for long-term storage and room-temperature storage of food products. Gas pack packaging is a tool that delivers long-term storage by filling a container with a gas such as nitrogen or carbon dioxide to inhibit the growth of bacteria and the like. Suitable films for gas pack packaging are gas barrier films with low oxygen permeability. As such gas barrier films, films that are formed by lamination of a resin with barrier properties and a polyolefine-based resin with low-temperature sealing properties are known.
For example, JP2000117872A (PTL 1) describes a film that has at least one layer made of a resin composition having gas barrier properties, balances gas barrier properties and drawability, and exhibits excellent heat-shrinkable properties. In addition, JPS588644A (PTL 2) describes a technique relating to a heat-shrinkable multilayer plastic film that provides a heat-sterilizable package with good gas barrier properties. Moreover, JP2008545558A (PTL 3) describes a technique directed to a multilayer film that has a biaxially oriented film formed by a layer of crystallizable polyolefin and at least one coextruded layer of ethylene-vinyl alcohol copolymers, and that is given sufficient mechanical properties.